A Comparative Analysis of Tear Strength Methodstear test is presented. As a result of the...

FIBRES & TEXTILES in Eastern Europe April / June 2004, Vol. 12, No. 2 (46)42 43FIBRES & TEXTILES in Eastern Europe April / June 2004, Vol. 12, No. 2 (46)

n IntroductionThe utility functions which fabrics should fulfil first of all depend on their destina-tion. Woven fabrics have a very wide range of applications, starting from un-derwear and everyday clothing, through protective and work clothing, decorative and furniture fabrics, up to technical tex-tiles. Such a wide range of application means that during their lifetime fabrics undergo actions from different forces and strains depending on their destination and working conditions [1].

They can be stretched in one direction (for example, safety and transportation belts) or in many directions (for exam-ple, furniture fabrics), torn (for example, elements of sleeves and trousers) or com-pressed (for example, rigid interlining). In most of the mentioned cases fabrics are used at least a few times, and some-times the number of work cycles can total many thousands of repetitions. In each work cycle, the total deformations are significant, and users expect that, after removing the forces, the fabric will return to its primary state [1].

The mechanical properties which most often decide their application onto a giv-en clothing fabric include unidirectional stretching, tear and elastic properties. The significance which the above-mentioned properties have for the utility of each fabric is obvious, but it is worth mention-ing that their role increases significantly, if we consider the criteria concerning the individual means of protection.

With Poland’s adaptation to EC require-ments, the law standardisation and nor-mative acts (EC directive 89/686/EWG) concerning individual protection include criteria which had to be fulfilled by protective and work clothing produced

A Comparative Analysis of Tear Strength Methods

B. Witkowska, I. Frydrych*

The Institute of Textile Materials Engineeringul. Gdańska 118, 90-520 Łódź, Poland

E-mail: [email protected]

*Technical University of Łódź ul. Żeromskiego 115, 90-924 Łódź, Poland

E-mail: [email protected]

AbstractFabric utility parameters most often depend on its mechanical properties. The most impor-tant strength parameters include unidirectional tensile strength, tear strength and elasticity properties. In this work we describe in detail the problem of tear strength, appropriate measurement methods and the correlation relationships between the results obtained by different tear methods. The measurements of tear strength were carried out for a chosen group of protective textiles. In addition, the unidirectional tensile strength was measured for the group of textiles mentioned above, and the correlation coefficients between the tensile strength and tear strength were calculated by different methods.

Key words: tear force, tearing strength, testing methods, static tearing, dynamic tearing.

in Poland. These requirements concern the uniforms of safety guard units. A danger to health and human life arises in many work situations in industry, such as welding, oil refinery work, and in the gas industry.

Uniforms and protective clothing, de-pending on their given destination, must fulfil many diverse specific requirements set down in special standards, which concern high mechanical strength, es-pecially tear and abrasion resistance. To assess tear strength in the application areas mentioned, both static and dynamic methods are used. Tear strength is a very important factor for the fabrics used on tents, tarpaulins, backpacks and for rec-reational purposes such as deckchairs, garden umbrellas and so on. A dynamic tear method also has an application for clothing fabrics, such as cotton fabrics destined for jeans.

In this paper, we describe in details the resistance to the action of static and dynamic tear force, the measurement methods and correlation relationships between the results obtained by differ-ent tear methods. Additionally, for the group of protective fabrics described, the tensile strength was assessed; we also present a trial for finding the correlation relationships between the tensile maxi-mum strength (more precisely, force) and the tear strength obtained by different measurement methods.

n Methodology The tear resistance of fabrics is a property which determines the material strength of an action of static force (a static tear test), kinetic force (a dynamic tear test) and tear test on a nail. The different methods of tear test procedure are reflected in dif-

ferent standards, which are characterised by different methods of sample prepara-tion, their shape and size, the way of clamping and the length of torn fabric distance, as well as the way of reading and calculating the tear force [2].

Below, we describe five static tear test methods and one dynamic method. All the methods (apart from method No. 1, also concerning the knitted fabrics, and method No. 5 for fabrics coated by gum and polymers) have been used for woven fabrics. They are not commonly applied for knitted and elastic fabrics. They are not appropriate for fabrics of high anisot-ropy or loose structure, because in these fabrics tearing most often occurs in a di-rection askew to the stretching direction.

We also took into consideration method No. 5 in our measurements, which al-though it concerns coated fabrics can also find application for testing the fire guard clothing.

The methods presented follow the fol-lowing standards:

§ No. 1 - PN-P-04640:1976 “Fabric measurement methods. Woven and knitted fabrics. Determination of tear strength”

§ No. 2 - PN-EN ISO 13937-2:2002 “Textiles - Tear properties of fabrics - Part 2: Determination of tear force of trouser – shaped test specimens (single tear method)” (ISO 13937-2:2000)

§ No. 3 - PN-EN ISO 13937-3:2002 “Textiles – Tear properties of fabrics - Part 3: Determination of tear force of wing-shaped test specimens (single tear method)” (ISO 13937-3:2000)

§ No. 4 - PN - EN ISO 13937-4:2002 “Textiles. Tear properties of fabrics - Part 4: Determination of tear force of


lounge - shaped test specimens (dou-ble tear test)” (ISO 13937-4:2000).

§ No. 5 - PN-P-04966:1993/A21:2002 “Rubber or plastics coated fabrics. Determination of tear force”

§ No. 6 - PN-EN ISO 13937:2002 “Textiles. Tear properties of fabrics - Part 1. Determination of tear force using ballistic pendulum method” (Elmendorf)” (ISO 13937-1:2000).

The above numbers are used for figure, graph and table description in the text.

Single tear methods Static methods (No. 1-5) differ from each other in sample preparation and clamp-ing, tearing direction in relation to the acting force, distance between jaws, and so on. The method of sample preparation is shown in Figure 1, but the method of clamping is shown in Figure 2.

Method No. 1 (according to PN-P-04640:1976) in December 2002 was replaced by PN-EN ISO 13937-2:2002. Additionally, No. 3 and No. 4 (decision no 57/2002 of the Polish Standardisation Commit-tee from 2002.12.23) were introduced as standardised methods. A description of the static tear methods is given in Table 1. In all the methods, the sample is torn at constant speed is maintained until the end of the measurement distance.

Static tear methods The differences in calculation of results, according to PN-P-04640:1976, accord-ing to the standard PN-EN ISO 13937:2002 Part 2, 3 and 4 and PN-P-04966:1993/AZ1:2002, should also be pointed out. The method of dividing the graph into intervals and the readings of force values for the above methods are shown in Figure 3.

Determination of tear forces for the methods so far applied (Figure 3a) relies on the graph’s division into 10 equal in-tervals along the tear (measurement) dis-tance in such a way that the beginning of the first interval corresponds to the first peak on the graph. Next, the maximum tear force corresponding to the highest peak is read at each interval. As a result, the mean tear force for both directions (longitudinal and reverse) and the maxi-mum tear force (mean from the highest peaks for n samples) for longitudinal and reverse directions are given.

In order to determine a tear force for the methods described in the standard

PN-EN ISO 13937:2002 Part 2, 3 and 4 (Figure 3b), the graph should be divided into four equal parts starting from the first and finishing on the last peak. The first part of the graph is not included in calculation of the mean value. Of the remaining three parts, the two highest and two lowest values are chosen. As a result, an arithmetic mean tear force for longitudinal and reverse directions from the chosen peaks is given. Additionally, the maximum tear force for longitudinal and reverse directions as a mean from maximum peaks is given. The standard PN-EN ISO 13937:2002 Part 2, 3 and 4 admits two ways of calculating results,

manually and by computer, which cannot give identical results.

Determining tear forces for the method according to PN-P-04966:1993/AZ1:2002 (Figure 3c) relies on determining the median from the five biggest tear forces for a given sample, for the middle part of graph, which consists 50% of the whole tear distance. Median values in both directions are given as a result.

Dynamic tear test The main element of the device for dynamic tear strength is a ballistic pendulum, by means of which force

Table 1. Description of static tear methods.

Method No.

StandardSingle

or double tearing

Tearing direction:

⊥or || to the acting force

Tearing distance,

mm

Measure-ment rate, mm/min

Distance between

jaws, mm

Shape of the

sample

A way of clamping the sample

1 PN-P-04640:1976 single ⊥ 40 ± 1 100 50 Fig. 1a Fig. 2a

2 PN-EN ISO 13937-3:2002 single || 75 ± 1 100 100 Fig. 1b Fig. 2b

3 PN-EN ISO 13937-3:2002 single ⊥ 75 ± 1 100 100 Fig. 1c Fig. 2c

4 PN-EN ISO 13937-4:2002 double || 75 ± 1 100 100 Fig. 1d Fig. 2d

5 PN-P-04966:1993/AZ1:2002 single || 145 ± 1 100 70 Fig. 1e Fig. 2e

Figure 2. Method of clamping the samples according to: a - PN-P-04640:1976, b - PN-EN ISO 13937-2:2002, c - PN-EN ISO 13937-3:2002, d - PN-EN ISO 13937-4:2002, e - PN-P-04966:1993/AZ1:2002.

Figure 1. Shape of samples according to: a - PN-P-04640:1976, b - PN-EN ISO 13937-2:2002, c - PN-EN ISO 13937-3:2002, d - PN-EN ISO 13937-4:2002, e - PN-P-04966:1993/AZ1:2002.


is suddenly applied to the appropri-ately prepared sample; the sample is then mounted between two jaws, one fixed and the second, movable one mounted to the device’s body. The movable jaw is connected to a pendulum, which falls down due to the gravimetric force, and the whole sample is torn by the displace-ment of the immobile jaw. In Figure 4, the Elmatear model 455 for the dynamic tear test is presented.

As a result of the measurement, the kinet-ic energy needed for the sample tear test along the initially cut distance is given. It is determined by the measurement of work done during the sample tear test on the tearing distance. The method of sam-ple preparation and its clamping in the jaws is shown in Figure 5. For clothing fabrics, the sample cut distance is 20±0.5 mm, and the tear distance is 43±0.5 mm. In the upper part of the sample, there is a notch which is used to avoid shredding the thread ends.

The advantage of the dynamic tear test is the option of quickly obtaining the results of the tear test (from readings directly on the device). In the case of the static methods, this is connected with reading the maximum and minimum val-ues from the graph, which in the case of a lack of electronic devices is very time-consuming.

n Comparative Measurements The hitherto used method according to PN-P-04640:1976 was replaced by PN-EN ISO 13937-2:2002, and furthermore part 3 and 4 of the above methods were introduced as standard methods. For these reasons, and also because a dy-namic tear method according to PN-EN ISO 13937-1:2002 and the method ac-

cording to PN-P-04966:1993/AZ1:2002 have not been used so far for clothing textiles (not coated), there is a need to carry out comparative measurements. On one hand, they allow the obtained results to be interpreted for methods not as yet applied, and on the other hand they an-swer the question of which relationships exist between the obtained results of tear strength methods [3,4].

Additionally, unidirectional strength measurements were performed according to PN EN ISO 13934-1:2002 “Textiles. Tensile properties of textiles. Part 1: Determination of maximum force and elongation at maximum force using the strip method” in order to determine the correlation between the maximum force results and the static or dynamic tear force. The comparative measurements were done in the Laboratory of Physical-Mechanical Properties in the Institute of Textile Material Engineering in Łódź.

The Instron tensile tester was used for the measurements. It fulfils all the standard requirements concerning the static tear test and unidirectional tensile strength. For dynamic measurements, we used the Elmatear device from the firm J.H. Heal which fulfils the requirements of standards concerning the dynamic tear strength. The measurements were carried out in the normal climate on the samples conditioned according to PN-EN 20139:1993. We measured the samples of five fabrics designed for the protective cloth-ing. The technical and technological fab-ric parameters are presented in Table 2. For the fabrics chosen for measurement, the tear test was performed by five static methods and one dynamic method; ad-ditionally, the unidirectional tensile strength was measured. For each direc-tion (warp-weft) we used 6 specimens.

As a result, we calculated the mean value (a) or median of tear forces in [N], the mean value (a) of maximum force in [N] and strain in [%] at the maximum force and values of random error (Ua) at the significance test level of α=0.05. The results of tear strength obtained, depend-ing on the method used, are presented in Table 3 and in Figure 6; the tensile strength results are presented in Table 4 and in Figure 7.

Figure 3. The way of reading tear forces according to: a - PN-P-04640:1976, b - PN-EN ISO 13937-2:2002, Part 2, 3 and 4, c - PN-P-04966:1993/AZ1:2002.

Figure 5. A method of sample preparation and of clamping in the Elmatear according to PN-EN ISO 13937-1:2002.

Figure 4. Elmatear device.


n Discussion of Results Kendall’s coefficient of agreement and correlation coefficient Analysing the values of the tear strength results obtained by the six different methods, we should note that the re-sults of the mean tear force (or median) for six methods are at different levels. Therefore, when starting the measure-ments, we should choose the appropriate measurement method by taking into ac-count the fabric’s destination, the kind of tear performance which can occur in the workplace, and also the parameters and criteria which are in the form of norma-tive documents for many fabrics.

In order to find the relationships between the results of mean tear forces (or median in method No. 5) for the six described methods, we calculated two Kendall’s agreement coefficients for five static tear methods and for all six methods (static and dynamic taken together). We wanted to check whether the tear results obtained by different methods are coherent. The ranking of 1 means the lowest mean value (or median) of tear strength, and the ranking of 10 is the highest [5,6].

We obtained the following values of Kendall’s agreement coefficients:§ for five static tear methods W1=0.868,

and§ for six tear methods (static and dy-

namic) W2=0.869.Considering that the value of the agree-ment coefficient can be changed within intervals (0;1), and that values close to +1 mean a high degree of agreement, it was stated that the values obtained confirmed quite a high degree of agreement of tear strength results. In addition, the linear correlation coefficients were calculated in order to confirm the relationships be-tween particular tear methods. Below are presented (Figure 6) the most interest-

ing figures from the methods where the results obtained represent the strongest and weakest correlation between them. All the correlation coefficients are set in Table 5.

The border value of the correlation coef-ficient at a random degree n-2=8, and the

significance level α=0.05, above which the correlation exists, is 0.632. Accord-ing to this, there is no linear correlation between methods 3 and 5 [7].

The high values of correlation coeffi-cients which we obtained, above 0.8 (ex-cept in 3 cases) confirmed a strong linear

Table 2. The set of technical-technological parameters of fabrics.

Characteristic Fabric A Fabric B Fabric C Fabric D Fabric E

Raw material 100% Cotton 100% Cotton 50% Poliester; 50% Cotton

90% Cotton10% Poliester 100% Cotton

Weave twill

twill

twill

twill

twill

Mass per unit area, g/m2 281 ± 5 247 ± 5 247 ± 5 230 ± 5 244 ± 5

Thread linear density, tex

warp 20 × 2 20 × 2 15 × 2 12 × 2 20 × 2weft 50 50 40 20 50

Number of thread per 10 cm

warp 342 ± 7 340 ± 7 490 ± 8 589 ± 8 342 ± 7weft 196 ± 6 192 ± 6 235 ± 7 321 ± 7 200 ± 6

Table 3. Tear strength results; a - mean value of the tear strength, Ua - value of random error.

Fabric

PN-P-04640:1976 PN-EN ISO 13937-2: 2002

PN-EN ISO 13937-3:2002

PN-EN ISO 13937-4:2002

PN-P-04966:1993/AZ1

:2002

PN-EN ISO13937-1:2002

Method 1 Method 2 Method 3 Method 4 Method 5 Method 6Static Dynamic

warp weft warp weft warp weft warp weft warp weft Warp wefta Ua a Ua a Ua a Ua a Ua a Ua a Ua a Ua median median a Ua a Ua

A 21.8 0.5 24.9 1.3 24.0 0.6 26.0 1.9 18.0 0.5 22.0 0.6 41.0 1.7 44.0 2.7 27.5 32.0 23.9 1.4 22.4 0.5B 32.5 0.5 36.8 2.2 44.8 3.5 39.6 0.6 28.3 1.3 34.0 1.3 76.9 5.5 74.0 2.4 68.8 51.0 49.6 5.1 44.3 3.7C 41.9 3.8 37.7 1.4 43.6 4.1 38.4 1.1 37.5 2.9 34.3 2.4 77.0 1.0 68.4 1.6 49.8 45.0 52.3 1.7 37.8 0.7D 31.4 0.8 27.5 3.9 27.8 1.2 24.5 1.2 28.4 1.7 22.4 1.4 49.5 0.7 45.8 3.6 40.0 37.5 25.3 1.2 19.1 0.9E 32.5 1.8 33.7 0.9 36.3 0.8 36.2 1.0 27.6 0.7 32.2 0.8 65.7 2.0 73.5 1.8 47.0 53.0 36.4 2.2 35.8 2.6

Figure 6. The most interesting correlation relationships between six tear methods.

r=0,984

10

20

30

40

50

20 30 40 50method 1

met

hod

3r=0,972

30

40

50

60

70

80

20 30 40 50method 2

met

hod

4

r=0,979

10

20

30

40

50

60

20 30 40 50method 2

met

hod

6

r=0,937

10

20

30

40

50

60

30 40 50 60 70 80method 4

met

hod

6

r=0,637

20

30

40

50

60

70

20 30 40 50method 1

met

hod

5

r=0,626

20

30

40

50

60

70

10 20 30 40 50method 3

met

hod

5


correlation relationship between the tear methods. It is worth noting some rules: § The strongest linear correlation coef-

ficient (above 0.9) is for methods No. 1 and No. 3; No. 2 and No. 4; No. 2 and No. 6; No. 4 and No. 6. All these methods have the same direction of tear force application in relation to the tearing direction. For methods No. 1 and No. 3, the tear test is carried out in the direction perpendicular to the direction of force application, and in methods No. 2 and No. 4 the tearing is carried out in the direction parallel to the force application. An interest-ing situation arises in methods No. 2 and No. 6, as well as No. 4 and No. 6. Method No. 6 concerns the dynamic tear test, so its procedure differs from the static tear tests described in meth-ods No. 2 and No. 4. Nevertheless, making the same assumptions, we can see certain similarities: . the method of sample mounting; the

clamping line in both methods is parallel to the torn sample threads,

. the action of the tear force; in the static method a successive force increase causes the breaking of threads in the tearing direction, and in the dynamic method there is a sudden force action on the similarly mounted threads, so the torn threads are broken simultaneously.

Taking the above into account, it can be assumed that in the case of methods No. 2 and No. 6, as well as No. 4 and No. 6 the tearing is carried out in the direction parallel to the direction of force applica-tion. This is confirmed by the high values of the correlation coefficients: 0.979 and

0.937. In the case of the method pairs No. 1 and No. 3, No. 2 and No. 4, No. 2 and No. 6, No. 4 and No. 6, a high value of linear correlation coefficient is observed for data in both measurement directions (warp and weft), as well as for each di-rection separately.§ The weakest linear correlation is be-

tween methods No. 1 and No. 5 and No 3 and No. 5. This is caused by two factors: . the directions of force application

are different. In methods No. 1 and No. 3 these are perpendicular, and in method No. 5 they are parallel to the force application.

. different method of calculating results. In methods No. 1 and No. 3, there is a division of the whole graph into intervals. In method No. 1 we have 10 intervals, and as a re-sult the arithmetic mean value from 10 maximum peaks of each interval is taken, whereas in method No. 3 we have a division into 4 intervals. As a result, the arithmetic mean value from two maximum and two minimum peaks for 3 intervals (the first is rejected) is taken (12 peaks in total). In method No. 5 we de-termine 5 maximum peaks for 50% of the middle part of the graph, and as a result, the median from these 5 maximum values is given.

Comparison of percent valuesIn order to find the practical plane of comparison for values obtained by the six methods of tear force measurement (which could be useful for the rapid laboratory interpretation of the results

obtained), the results obtained by method PN-P-04640:1976 (method No. 1) were assumed as 100%. The results obtained by the other methods were presented in relation to the recommended (base) result (Figure 7).

Method No. 1 was chosen as a base be-cause it was withdrawn and replaced (by the Polish Standardisation Committee) by method No. 2 (PN-EN ISO 13937-2:2002), but the majority of the tear resist-ance parameters concerning fabrics for different destinations were determined by method No. 1. In fact, while testing the samples according to the new stand-ards, it is necessary to properly interpret the results obtained in relation to the pa-rameter value.

It is difficult to unequivocally interpret the values obtained in percent; never-theless, it is worth noting some rules of relationships:§ The results for fabrics A, B, C and

E obtained by method No. 2 are at the level of about 107% of the base result (104 to 112%). The exception is a tear force in a warp direction for fabric B, which achieves 138% of the base result. Nevertheless, looking at the tear results for warp in the case of fabric B, it is worth noting that in methods No. 4, No. 5 and No. 6 this fabric obtained the highest percentage values. This may confirm the high tear strength of warp thread in fabric B. In addition, it was observed for fabric B that in the cases of methods No. 1 and No. 3 the mean tear force for a warp is lower than the mean tear force of the weft, and for the results obtained by methods No. 2, No. 4, No. 5 and No. 6 for the same fabric, the mean force (or the median in the case of method No. 5) is higher than the mean tear force for the warp. Similar differ-ences were observed for fabric E. For methods No. 1, No. 3, No. 4 and No. 5, the results we obtained for weft tear forces were higher than analogous for warp tear forces; whereas for methods No. 2 and No. 6, we achieved the bet-ter results for the warp. Nevertheless, in the case of fabric E it can be noted that the results obtained for warp and weft are on the similar level. Taking into account the upper value of the confidence limit for warp in methods No. 2 and No. 6 the tear strength val-ues obtained confirm the higher weft tear strength for fabric E.

§ The results obtained by method No. 3 are on the same level, i.e., ca. 90%

Table 4. Results of tensile strength test; a - mean value, Ua - value of random error of the value a.

FabricMaximum force, N Strain at the maximum force, %

warp weft warp wefta Ua a Ua a Ua a Ua

A 940 80 590 60 8.5 0.5 17.5 1.0B 1100 100 630 40 10.5 0.5 19.5 0.5C 1200 100 650 10 24.5 2.5 14.0 1.0D 1600 100 870 60 19.0 15.5 15.5 0.5E 1200 100 840 10 12.5 0.5 23.0 2.5

Table 5. The correlation coefficients between results of different tear methods.

Methods Correlation coefficient r Methods Correlation

coefficient r Methods Correlation coefficient r

1 and 2 0.839 2 and 3 0.818 3 and 5 0.6261 and 3 0.984 2 and 4 0.972 3 and 6 0.7881 and 4 0.861 2 and 5 0.883 4 and 5 0.8841 and 5 0.637 2 and 6 0.979 4 and 6 0.9371 and 6 0.814 3 and 4 0.861 5 and 6 0.843


(from 83 to 96%) of the base result for all the fabrics measured. Taking into account the strong linear correlation which exists between methods No. 1 and No. 3 (r=0.984), it can be suggest-ed that method No. 3 could substitute for method No. 1.

§ The results for fabrics A, B, C and E obtained by method N. 4 are at a level two times higher (177% to 237%) than those obtained by method No. 1. For fabric D, the results are at a level ca. 160% of the base result; neverthe-less, this fabric was characterised by lower yarn linear densities.

§ Most difficult is the interpretation of results obtained by methods No. 5 and No. 6. There are big deviations in per-centage results in relation to the base result. For method No. 5, values from 119 to 212% were noted. Similarly, for the method No. 6, results were ranged from 69% (fabric 4) to 153%.

To sum up, it should be pointed out that this form of result interpretation could in practice be useful, because by making

measurements with the chosen method we could obtain an approximate informa-tion on which level a result obtained by a different method would be. Neverthe-less, upon analysing the results for five fabrics we can not state unequivocally whether such an interpretation would be useful for a bigger sample popula-tion, nor whether any kind of ‘anomaly’ (e.g. for the same fabric, the result for the warp direction can be once higher and once lower than for the weft direction) is due to the yarn strength uniformity, or whether it is a regularity, which can occur for some fabrics of given technological parameters.

Comparison with the tensile strength resultsIn order to establish the relationships between the particular tear methods and tensile strength, the linear correlation co-efficients were calculated. The results ob-tained are presented in Table 6. The very low values of correlation coefficients (0.007 to 0.138) which were obtained confirmed that there was no correlation between these measurements.

n Conclusions On the basis of the results obtained, the following conclusions were drawn:§ Considering the rank coefficient of

agreement, a coherency was shown between all the static tear test methods (W1=0.868), as well as between static methods and the dynamic method (W2=0.869).

§ The following points were proved:. there is a high value of linear cor-

relation relationship for methods of the same direction of force applica-tion in relation to the tearing direc-tion (r=0.9),

. a good correlation for the rest of the methods (r= 0.626-0.884).

§ There are some similarities between static tear methods, in which the di-rection of force application is parallel to the tearing direction, and a dynamic tear method, as is confirmed by the high value of correlation coefficients between these methods (r=0.9)

§ A lack of linear correlation relation-ship between the static or dynamic tear strength and the tensile strength was demonstrated.

References 1. W. Żurek, K. Kopias, Structure of Flat

Textile Products, WNT, Warsaw 1977 (in Polish).

2. T. Żyliński, Textile Metrology, t.II. “Editor of light and Nutri five Industry.” Warsaw (1965).

3. B. Witkowska, I. Frydrych, Clothing fabrics – static tear strength methods, Przegląd Włókienniczy No. 6, (2003).

4. B. Witkowska, I. Frydrych, Dynamic tear strength method and its correlation with the static methods, Przegląd Włókienni-czy No. 8, (2003) (in printing).

5. G. Udny Yule, M.G. Kendall, Introduction to the statistics theory, PWN, Warsaw 1966.

6. M. Grudniewski and co, Calculations in textile metrology, the Technical University of Łódź, Łódź 1974.

7. W. Volk, Applied Statistics for Engineers, WNT, Warsaw 1973.

8. PN-EN ISO 13937-2:2002 “Textiles. Tensile Properties of Fabrics - Part 1: Determination of maximum force and elongation at maximum force using the strip method” (ISO 13934-1:1999).

9. PN-P-04640: 1976 “Fabric measurement methods. Woven and knitted fabrics. De-termination of tear strength”.

10. PN-EN ISO 13937:2002. “Textiles. Tear properties of fabrics - Part 1. Determina-tion of tear force using ballistic pendulum method (Elmendorf)”.

11. PN-P-04966:1993/AZ1:2002 “Textiles. Tear properties of fabrics - Part 2: Deter-mination of tear force of trouser - shaped test specimens (Single tear method).

12. PN-EN ISO 13937-3:2002 “Textiles. Tear properties of fabrics - Part 3: Determi-nation of tear force of wing-shaped test specimens (single tear method)” (ISO 13937-3:2000).

13. PN-EN ISO 13937-4:2002. “Textiles. Tear properties of fabrics - Part 4: Determina-tion of tear force of lounge - shaped test specimens (Double tear test)”.

14. PN-P-04966:1993/A21:2002 “Rubber or plastics coated fabrics. Determination of tear force”.

0

5

10

15

20

25

30

35

40

45

50

warpweft

100 110 10483 88

188 177

126 129

110 90

0

20

40

60

80

warpweft

100138 108

87 92

237 201 212 139

153 120

0

20

40

60

80

warpweft

100 104 102 89 91

184 181

119 119 125 100

0

20

40

60

warpweft

100 89 89 90 81

158 167127 136

81 69

0

20

40

60

80

1 2 3 4 5 6Method

warpweft

100 112 10785 96

202 218

145 157

100 110

Tear

forc

e,N

Tear

forc

e,N

Tear

forc

e,N

Tear

forc

e,N

Tear

forc

e,N

1 2 3 4 5 6Method

1 2 3 4 5 6Method

1 2 3 4 5 6Method

1 2 3 4 5 6Method

a) b)

d)c)

e)

Table 6. The values of linear correlation between tear forces and tensile strength.

Tear strength methods

Correlation coefficient r

1 0.1072 0.0413 0.0544 0.0075 0.1386 0.078

Figure 7. Results of tear strength for warp and weft depending on the method for five chosen fabrics; a - fabric A, b - fabric B, c - fabric C, d - fabric D, e - fabric E.

Received 14.05.2003 Reviewed 02.02.2004

A Comparative Analysis of Tear Strength Methodstear test is presented. As a result of the...

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Transcript of A Comparative Analysis of Tear Strength Methodstear test is presented. As a result of the...